1. Field of the Invention
The present invention relates to a flow divider for dividing a fluid flow into a number of fluid flows, in particular for analytical or preparative fluid measurement technology and/or for micro-fluid systems, which has at least one working sensor assigned to one of the fluid flows and which comprises a control unit for regulating the pressure of one of the fluid flows and/or one of the fluid flows, which is coupled to one or each working sensor and an actuator for altering this fluid flow.
2. Discussion of the Background Art
Flow dividers designated as splitters are used in analytical or preparative fluid measurement technology, in particular in association with devices for generating and supplying fluid volume flows in capillaries, preferably in chromatographic separating columns for analytical fluid separating technology. A first application comprises dividing the entire flow generated and supplied by a pump into at least two partial flows, an excess flow in an excess path and a working flow in a working path. In the process the desired working flow in the separating column is adjusted and provided by means of so-called restrictors, that is, by hydraulic resistors arranged in the excess path. To maintain the working flow, that is, the volume flow flowing through the capillaries, substantially constant, depending on the pressure conditions and/or volume conditions in the working path changing as a result of disturbances, for example, DE 199 14 358 A1 discloses a device and a process for providing fluid volume flows in capillaries, which exhibits at least one working sensor and a control unit for regulating the working flow and/or the pressure in the working path, whereby the control unit is coupled to the working sensor and a means for altering the working flow. This device enables the pressure and/or the working flow to be measured and kept constant advantageously in the working path, yet allows this device no corresponding possibilities and measures in the other splitter branch, that is, the excess path in this case.
Another preferred application of such splitters in analytical or preparative fluid measurement technology and/or micro-fluid technology comprises splitting the fluid coming through the separating column or the separating channel into two or more fluid flows, so that these can be supplied to fraction collectors and/or mass spectrometer detectors arranged downstream. Passive splitters are used chiefly for this, that is, individual elements which exhibit a different hydraulic flow resistance. Splitters with back pressure controllers have also become known, whereby the back pressure is kept constant in one of the split branches only. Individually it cannot be avoided that the volume flow changes depending on the physical properties of the fluid and the fluctuations in pressure in each other splitter.
It is accordingly an aim of the invention to make available a flow divider having a reduced back pressure sensitivity, enabling the splitting ratio to be kept constant independently of the physical properties of the fluid and/or the fluctuations in pressure.
This task is solved according to the present invention by the features of claim 1, in particular in that at least a number of working sensors corresponding to the number of divided fluid flows is provided, whereby respectively at least one of the working sensors is assigned to one of the fluid flows and whereby the working sensors enable recording or measuring of the respective fluid flow assigned to this working sensor.
With the flow divider according to the present invention the volume of the splitter branches can be adjusted according to the splitting ratio such that the fluid front respectively progresses parallel. In this way media-specified breakdowns occur isochronously so that they can be compensated.
The foregoing measures enable the split ratio between each two of the fluid flows to be precisely specified and/or be kept constant. By at least a number of the working sensors assigned to the affected fluid flows corresponding to the number of divided fluid flows being provided, the splitter according to the present invention can be operated independent of media, that is, the split ratio and/or the volume flow can be kept constant in at least one splitter branch independently of the physical properties of the fluid. In contrast to the passive splitters known from the prior art, in which the split ratio is either unknown or detectable only by expensive calibrating, the splitter according to the present invention concerns an active splitter. Via the abovementioned measures the principal drawback of the passive splitters known from the prior art, namely the back pressure sensitivity, can be decreased or completely eliminated. Such active splitters are also distinguished by a greater application flexibility, as they can be employed in all areas where a number of partial flows is to be split off from a single fluid flow.
With the flow divider according to the present invention and realised as an active splitter a fluid flow or influx can be divided into two to n partial flows. The ratio of the individual partial flows can either be firmly preset or adjusted according to the user and application requirements. Typical values for the splitter ratios realisable with such active splitters are 1:1 to 1:10000. It is understood that nxe2x88x921 partial flows can also be split off using the flow divider according to the present invention.
The number, arrangement and type according to the present invention of the working sensors enable different properties of the fluids flowing through the flow divider, for example their viscosity or thermal capacity, to be compensated advantageously and calculated by means of a computer unit coupled to the control unit. In this way the widest range of measuring principles, such as for example differential pressure measurement or thermal processes, can be utilised advantageously. This is particularly beneficial because for the preferred flow region between approximately 10 nl/min to approximately 1000 ml/min, in particular from 1 nl/min to 100 ml/min, no direct measuring processes independent of the properties of the fluids are known to date and because frequently calibration is not possible, as the fluid mixtures being worked with are unknown.
It is effective here if the working sensors are designed as flow sensors directly measuring the fluid flow, in particular as thermal or thermally pulsed mass flow rate meters or as volumetric flow rate meters. This enables a comparatively simple structure for the flow divider and a comparatively simple computer evaluation of the measurement signals, because in this case the splitter ratio can be determined directly by simple relational development of the measuring values.
In the case where the flow divider is provided with such working sensors whose measurement signals depend on the physical properties of the fluid flowing through the flow divider and whose flow rate or volume flow is to be determined, working sensors are to be provided which are of identical design in this respect.
At least one of the working sensors is assigned advantageously to each of the divided fluid flows. The splitting ratio can be determined directly and/or kept constant particularly easily by this.
If an adjustable actuator for changing the respective fluid flow is assigned to each of the divided fluid flows, the splitting ratio and thus the volume flow can be kept constant in each branch. Sample analysis can be performed parallel in each branch by this, enabling a particularly economical method of operation.
It is effective, if the actuator or each actuator exhibits a continuously changeable hydraulic flow resistance. Electromagnetic regulating valves and/or temperature-controlled actuators can be used, by way of example. Independently of whether variable restrictors adjustable step by step or continuously adjustable are used, they must have an adequate dynamic range, that is, the flow resistance must be adjustable in correspondingly broad limits in order to be able to equalise the possible external fluctuations in back pressure, dependent of the respective applications, by corresponding change of the hydraulic resistance.
According to a preferred field of application the flow divider is effectively arranged such that it enables division into fluid flows in a range of application or working sphere of approximately 10 nl/min to approximately 1000 ml/min, whereby applications to a microrange of approximately 1 nl/min are conceivable, if required.
The present task is solved also by a process for dividing a fluid flow into a number of fluid flows, in particular in analytical or preparative fluid measurement technology and/or in micro-fluid systems, whereby a control unit which is coupled to at least one working sensor, which is assigned to one of the fluid flows, and to an actuator for changing this fluid flow, regulates the pressure of one of the fluid flows and/or regulates one of the fluid flows, characterised in that by means of at least a number of working sensors corresponding to the number of divided fluid flows, of which respectively at least one is assigned to one of the fluid flows, the respective fluid flow is measured and whereby the control unit regulates the fluid flows such that the ratio between at least two of the fluid flows remains substantially constant.
The abovementioned characteristics contribute both individually and in any combination to diminishing the back pressure sensitivity when one fluid flow is divided into a number of fluid flows, and enable the volume flow to be kept constant independent of the physical properties of the fluid assigned thereto and the fluctuations in pressure in this fluid in at least one splitter branch.